512 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Panicum TRIGONUM Retz.,! an East Indian perennial with low creeping and 
branching culms and spreading pilose blades 2 to 4 cm, long, contracted panicles of 
short-pediceled hispidulous spikelets about 1.7 mm. long, the second glume keeled, 
the fruit slightly compressed laterally, has been found ‘‘under the shade of a shrub,” 
Port of Spain, Trinidad, Broadway 4891. 
Subgenus DICHANTHELIUM Hitchc. & Chase. 
Foliage soft and lax, the flat blades prominently ciliate; 
plants branching from the base, finally forming ro- 
settes or cushions. ....-----.22.-22--2e-eee eee eee See Laxrrtora, p. 513. 
Foliage not soit and lax; plants branching from the culm 
nodes. 
First glume nearly as long as the spikelet..-.--..--- See Corpovensla, p. 525. 
First glume much shorter than the spikelet. 
Spikelets glabrous; plants glabrous throughout; 
autumnal form erect, not bushy-branching. See Dicnoroma, p. 516. 
Spikelets pubescent. , 
Sheaths glabrous or minutely puberulent 
only; ligules minute or obsolete. 
Spikelets attenuate at base, mostly 
prominently pustulose; blades 
narrow, stiff, strongly nerved, ta- 
pering from base to apex......-. See ANaustirota, p. 514. 
Spikelets not attenuate at base, not pus- 
tulose. 
Spikelets subglobose or pyriform. 
Blades spreading, rarely over 5 
cm. long and 5 mm. 
wide, spikelets pyriform; 
autumnal form bushy- 
branching ......-..----- See LANCEARIA, p. 522. 
Blades erect, 7 to 13 cm. long, 
7 to 14 mm. wide; spike- 
lets spheroid ........... See SPHAEROCARPA, p. 521, 
Spikelets not subglobose nor pyri- 
form. 
Spikelets 2.8 mm. or more long. See Commutata, p. 524. 
Spikelets not over 2 mm. long. 
Blades with a cartilaginous 
white margin; spike- 
lets not over 1.5 mm. 
long .......-...---- 101. P. albomarginatum. 
Blades not white-margined ; 
spikelets 2mm. long. See Dichoroma, p. 516. 
Sheaths pubescent. 
Spikelets 4 mm. long, pyriform....--.. 104. P. nodatum. 
Spikelets not over 2.6 mm. long. 
Spikelets attenuate at base, mostly 
prominently pustulose; blades 
narrow, stiff, strongly nerved, 
tapering from base to apex; 
autumnal form often bushy- 
branched... .....-...------ See ANGUSTIFOLIA, p. 514. 
1Obs, Bot, 3:9. 1783, 
